Edition of a node revision with Entity Translation language switcher

Problem/Motivation

On the edition page for a node revision, using Entity Translation for node translation, there is no language switcher (in the secondary tabs) like in the node edit page.

Requirement

Entity Translation (using 7.x-1.0-beta4) enable and a content-type using both ET and State Flow.
Language detection using URL method (prefix) for content-type, and all site languages (at least 2) must have a prefix define.
At least one field in the content-type must be translatable.

(Optional)
In my case I have enabled the Title module and replace the content-type title by a field title. The field translation was activated.

Steps to reproduce

1. Create a content in English, and save "to draft" (e.g. with content-type Basic page).
2. Add a translation in French and keep it at draft state. (ET language switcher exist)
3. Update the French translation and publish the content. (ET language switcher exist)
4. Again update the French translation and set its status to draft. (ET language switcher exist)
5. Once again update the French translation. This time the ET language switcher will not appear.

Proposed resolution

TL;DR: Add Entity Translation language switcher to node revision edit page.

The issue appear because the page callback of the path 'node/%node/edit' was alterated. It's important to preserve the concept add with this alteration: user always edit the active revision of a node.
The workaround I propose start with removing this alteration. Preciselly, I moves its concept in a hook_inbound_url_alter.
This way the node page handle node content only and node revision page handle node revision content (beside the url path looking like node page).
For now I just moves some code and change some process a little bit. But my main purpose was to add language switcher.
To do so, I create an Entity Translation handler dedicated to node revision. Using the custom page create by State Flow module to edit node revision.

But, yes there is a but...

Remaining tasks

On the node revision edit page, there is no primary tabulations. See the issue 1493638 and comment #5.

If you find these feature request interesting, I will gladly pursue my effort.

Finally, big thanks for the module and the great work on the 3.x version.